Views: 7 Author: Monica Publish Time: 2026-04-17 Origin: Site
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ASTM A815 UNS S32750 - also called 2507 super duplex - pipe fittings were supplied to a Brazilian industrial client for offshore and petrochemical pipeline service and shipped to the Port of Santos. This case study documents the grade, the standards applied (ASTM A815, ASME B16.9, ASME B16.25) and the quality evidence (MTR, PMI, NDE) that accompanies every JN ALLOY super duplex order.
Quick answer: UNS S32750 is a 25% chromium super duplex stainless steel with a pitting resistance equivalent number (PREN) above 40. Its combination of a 550 MPa minimum yield strength and chloride stress-corrosion-cracking resistance is why Brazilian operators specify it for pre-salt offshore and refining duty.
Quick reference - ASTM A815 UNS S32750 super duplex fittings
Attribute | Value |
|---|---|
Grade (UNS) | S32750 (also called 2507, 1.4410, F53) |
Product form | Butt-weld pipe fittings (ASTM A815) |
Chromium | 24.0 - 26.0 % |
Molybdenum | 3.0 - 5.0 % |
Nitrogen | 0.24 - 0.32 % |
PREN (min) | Above 40 (typically 40 - 42) |
Min. yield strength | 550 MPa (80 ksi) |
Min. tensile strength | 795 MPa (115 ksi) |
Key standards | ASTM A815, ASME B16.9, ASME B16.25 |
Destination | Port of Santos, Brazil |
ASTM A815 covers wrought austenitic-ferritic (duplex) stainless steel piping fittings intended for pressure piping systems. UNS S32750, commercially known as 2507, is the highest-alloy duplex grade in routine pipeline service and the focus of this Brazil shipment.
Duplex stainless steels have a roughly equal austenite and ferrite microstructure. That two-phase balance gives S32750 roughly twice the yield strength of 316L while keeping the chloride resistance that austenitic grades lack. The grade is also listed as 1.4410 in EN 10088 and as F53 in the UNS-forgings cross-reference. Review the full material profile on our what is super duplex S32750 and properties of S32750 pages.
For the Brazil order, fittings were produced as butt-weld elbows, pipe bends and a concentric reducer to ASTM A815, dimensioned to ASME B16.9 with ends prepared to ASME B16.25. The nominal chemistry and mechanical minimums are shown below and are the basis for the material test reports issued with the shipment.
Table 1. Chemical composition of UNS S32750 (cast and analysis, per ASTM A815/A790)
Element | Composition, % max (range where given) |
|---|---|
Carbon (C) | 0.030 max |
Manganese (Mn) | 1.20 max |
Phosphorus (P) | 0.035 max |
Sulfur (S) | 0.020 max |
Silicon (Si) | 0.80 max |
Chromium (Cr) | 24.0 - 26.0 |
Nickel (Ni) | 6.0 - 8.0 |
Molybdenum (Mo) | 3.0 - 5.0 |
Nitrogen (N) | 0.24 - 0.32 |
Copper (Cu) | 0.50 max |
Table 2. Mechanical properties of solution-annealed UNS S32750 (per ASTM A815)
Property | Minimum value |
|---|---|
Tensile strength | 795 MPa (115 ksi) |
Yield strength (0.2% offset) | 550 MPa (80 ksi) |
Elongation in 2 in. | 15 % |
Hardness | 310 HB / 32 HRC max |
Density | 7.8 g/cm3 |
Against the more common 2205 duplex (S32205), S32750 adds chromium, molybdenum and nitrogen, which lifts PREN from roughly 35-38 to above 40 and raises the minimum yield strength from 448 MPa to 550 MPa.
That difference is what decides grade selection in chloride-rich, high-pressure service. Where 2205 is adequate for milder seawater cooling systems, S32750 is specified when the duty involves hot chloride, CO2 and H2S, or where wall thickness must be minimised. The comparison below uses minimum chemistry and PREN; mechanical minimums should always be confirmed against the current ASTM edition. See also duplex S31803 and duplex S32205.
Table 3. UNS S32750 vs other common duplex grades
Grade (UNS) | Cr % | Mo % | N % | PREN | Min. yield MPa | Positioning |
|---|---|---|---|---|---|---|
S31803 (2205, 1st gen) | 21-23 | 2.5-3.5 | 0.08-0.20 | ~34-35 | 450 | Entry-level duplex |
S32205 (2205) | 22-23 | 3.0-3.5 | 0.14-0.20 | ~35-38 | 448 | Standard 2205 workhorse |
S32750 (2507) | 24-26 | 3.0-5.0 | 0.24-0.32 | >40 | 550 | Super duplex, high PREN |
S32760 (Zeron 100) | 24-26 | 3.0-4.0 | 0.20-0.30 | >40 | 530 | Super duplex + W and Cu |
Brazil's hydrocarbon reserves lie in the pre-salt (pre-sal) province beneath the Campos and Santos Basins, where production happens at water depths of 2,000 m or more in chloride-rich, high-pressure, CO2-bearing fluids.
In that environment, ordinary austenitic stainless and even 2205 duplex can be out of their comfort zone. UNS S32750's PREN above 40 and its resistance to chloride pitting and stress corrosion cracking make it the defensible choice for topside piping, risers, flowlines and process skids. The client's project schedule also demanded reliable, documented supply - which is where the quality package below mattered.
Chloride-rich seawater and produced water at extreme water depths
High operating pressure and mechanical loads on subsea and topside piping
CO2 and, in sour fields, H2S exposure governed by NACE MR0175 / ISO 15156
Need for thinner, high-strength walls to reduce weight and weld volume
Brazil's pre-salt (pre-sal) province was opened after major discoveries in 2006 and now accounts for the majority of the country's oil output. Reservoirs sit 2,000 m or more below the seabed, beneath thick salt layers, in waters that are both deep and warm. That combination - high chloride, dissolved CO2, occasional H2S and high pressure - is exactly the duty envelope where 2507 super duplex is specified over leaner duplex and austenitic grades.
Like other duplex grades, S32750 is welded with controlled heat input to preserve the ferrite-austenite balance and to avoid intermetallic (sigma) phase formation, which would otherwise rob the joint of toughness and corrosion resistance.
Typical practice uses no preheat, a maximum interpass temperature around 150 C, and filler metals that are overalloyed in nickel and nitrogen (for example ER2594 / 25.10.4.L) so the weld metal matches the corrosion resistance of the base metal. Post-weld heat treatment is generally not required, and the weld area is usually examined by PT or MT after cooling. Because the ferritic phase in duplex is ferromagnetic, MT is a practical option here, whereas on fully austenitic stainless it is not.
Control heat input and keep interpass below about 150 C to limit sigma phase
Use overalloyed duplex filler (ER2594 class) for corrosion-matched welds
No preheat and usually no post-weld heat treatment
Examine welds by PT, with MT applicable because duplex is partly ferromagnetic
The fittings were manufactured to ASTM A815 and dimensioned to ASME B16.9, with weld ends prepared to ASME B16.25. Where the service is sour, NACE MR0175 / ISO 15156 is the controlling reference for material selection.
Dimensional inspection followed ASME B16.9 tolerances (out-of-roundness, wall-thickness and end-squareness), and duplex-specific checks - in particular intermetallic (sigma) phase control per ASTM A923 - were part of release. The governing documents for this order are listed below.
Table 4. Standards applied to the Brazil super duplex fitting order
Document | Scope |
|---|---|
ASTM A815 / A815M | Wrought austenitic-ferritic (duplex) stainless steel piping fittings |
ASME B16.9 | Factory-made wrought butt-welding fittings - dimensions and tolerances |
ASME B16.25 | Butt-weld end preparation (bevel geometry) |
NACE MR0175 / ISO 15156 | Sulfide stress-cracking resistance for sour (H2S) service |
ASTM A370 | Mechanical test methods and definitions for steel products |
ASTM A923 / A262 | Detection of detrimental intermetallic (sigma) phase in duplex |
Every fitting was released against an EN 10204 material test report, verified by positive material identification (PMI), and examined by liquid-penetrant (PT) inspection; the ferritic phase in duplex also permits magnetic-particle (MT) examination.
To remove doubt for the client's quality team, JN ALLOY supplied full MTRs, third-party inspection certificates and conformance documentation for the ASME B16.9 and B16.25 requirements. Goods were then seaworthy-packaged for the long transit from China to the Port of Santos.
EN 10204 3.1 / 3.2 material test report (MTR) with actual heat chemistry
PMI (XRF or OES) to confirm UNS S32750 chemistry on each batch
Surface examination by PT, with MT applicable because duplex is partly ferromagnetic
Third-party inspection (for example SGS, BV or TUV) available on request
Visual and dimensional inspection to ASME B16.9; anti-rust, seaworthy export packaging
The order comprised butt-weld fittings produced to ASTM A815 UNS S32750, dimensioned to ASME B16.9 with ends to ASME B16.25. The itemised list is preserved exactly as supplied.
Order record - ASTM A815 UNS S32750 butt-weld fittings supplied to Brazil
Item | Qty | Description |
1 | 2 | 45° Long Radius Elbow, ASME B16.9, Butt Weld ASME B16.25, DN 4in, Sch 40S |
2 | 2 | 90° Long Radius Elbow, ASME B16.9, Butt Weld ASME B16.25, DN 4in, Sch 40S |
3 | 2 | 90° Short Radius Pipe Bend, ASME B16.9, Butt Weld ASME B16.25, DN 2½in, Sch 40S |
4 | 1 | 45° Long Radius Elbow, ASME B16.9, Butt Weld ASME B16.25, DN 2in, Sch 40S |
5 | 1 | U-Type Round Clamp, ASTM A193 Gr. B7, Zn-Ni Coated, Vulcanized Rubber, DN 14in Pipe |
6 | 5 | 90° Long Radius Pipe Bend, ASME B16.9, Butt Weld ASME B16.25, DN 12in, Sch 40S |
7 | 1 | Concentric Reducer, ASME B16.9, Butt Weld ASME B16.25, DN 6×4in, Sch 40S, Uncoated |
8 | 1 | Sea Freight Costs & Charges to Brazil (Port of Santos) |
For related product lines, see our butt-weld pipe fittings, steel pipe and tube and flanges pages. The same grade is also available as super duplex S32750 plate and super duplex S32760 for adjacent scopes.
S32750 fittings are specified wherever chloride and pressure combine: offshore and subsea piping, desalination, flue-gas desulfurisation, heat exchangers and chemical processing.
Offshore and subsea production systems, risers and flowlines - see oil and gas applications
Desalination and seawater handling - see marine engineering
Petrochemical and acid-processing plants - see chemical equipment
Heat exchangers and pressure vessels - see S32750 heat exchangers
What is UNS S32750 super duplex stainless steel?
UNS S32750, commercially known as 2507, is a 25% chromium, roughly 4% molybdenum and 7% nickel duplex stainless steel. Its pitting resistance equivalent number (PREN) is above 40, which is why it is classed as a super duplex grade and used in chloride-rich, high-pressure service.
What is the difference between S32750 and S32205 duplex?
S32750 contains more chromium, molybdenum and nitrogen than the standard 2205 duplex (S32205). That raises PREN from about 35-38 to above 40 and lifts the minimum yield strength from 448 MPa to 550 MPa, so S32750 is chosen for harsher chloride and sour-service duty.
What standards cover ASTM A815 UNS S32750 butt-weld fittings?
The fittings are produced to ASTM A815, dimensioned to ASME B16.9 and prepared with ends to ASME B16.25. For sour (H2S) service, material selection is governed by NACE MR0175 / ISO 15156.
Why is super duplex used in Brazil's offshore oil and gas?
Brazil's pre-salt fields sit under 2,000 m or more of water in chloride-rich, high-pressure, CO2-bearing fluids. UNS S32750's PREN above 40 and resistance to chloride stress corrosion cracking make it a defensible choice for offshore and refining piping.
What quality documents accompany a super duplex fitting order?
Each order ships with an EN 10204 material test report (MTR), positive material identification (PMI) and liquid-penetrant (PT) inspection, with magnetic-particle (MT) also applicable because duplex is partly ferromagnetic. Third-party inspection certificates are available on request.
What is the PREN of UNS S32750?
PREN is calculated as percentage chromium plus 3.3 times percentage molybdenum plus 16 times percentage nitrogen. For UNS S32750 the result is typically 40 to 42, with a specification minimum above 40.
UNS S32750 (2507) is a super duplex stainless steel with PREN above 40 and 550 MPa min yield.
It was selected for Brazil because pre-salt offshore duty is chloride-rich and high-pressure.
Fittings were built to ASTM A815, ASME B16.9 and ASME B16.25, with ends to B16.25.
Each order ships with MTR, PMI and NDE evidence, plus optional third-party inspection.
For thinner, lighter, corrosion-resistant piping, S32750 beats 2205 duplex on both PREN and strength.
ASTM A815 / A815M - Standard Specification for Wrought Austenitic-Ferritic Duplex Stainless Steel Piping Fittings
ASME B16.9 - Factory-Made Wrought Buttwelding Fittings
ASME B16.25 - Buttwelding Ends
NACE MR0175 / ISO 15156 - Petroleum and natural gas industries - materials for use in H2S-containing environments
ASTM A923 - Detecting Detrimental Intermetallic Phases in Duplex Stainless Steels
Authored by Monica. Technical review by JN ALLOY Technical Department. Originally published 2026-04-17; last updated 2026-09-30. JN ALLOY supplies ASTM A815 UNS S32750 super duplex fittings with full mill and inspection documentation - contact us at jnalloy.com/contactus for project pricing.
Super duplex UNS S32750 butt-weld pipe fittings - elbow and concentric reducer supplied to Brazil
ASTM A815 UNS S32750 super duplex fittings ready for export to Brazil
